Variable geometry muffler for an exhaust system of an internal combustion engine

ABSTRACT

A variable geometry muffler for an exhaust system of an internal combustion engine; the muffler displays: a tubular body, which displays an inlet opening, an outlet opening and a labyrinth which determines a path for the exhaust gases from the inlet opening to the outlet opening; and a bypass valve, which is arranged within the tubular body to modify the geometry of the labyrinth according to the exhaust gas pressure; the bypass valve displays a lid, which is coupled to a bypass opening and is mobile from a closed position of the bypass opening to an opening position of the bypass opening by effect of the exhaust gas pressure and against the bias of an elastic body which tends to maintain the lid in the closed position; the elastic body consists of an elastic foil, which is folded as a “U” and displays a mobile end which supports the lid and a fixed end which is opposite to the mobile end and which is integral with a fixed part of the muffler.

TECHNICAL FIELD

The present invention relates to a variable geometry muffler for anexhaust system of an internal combustion engine.

BACKGROUND ART

An internal combustion engine is provided with an exhaust system, whichhas the function of introducing into the atmosphere the gases producedby the combustion limiting both the noise and the content of pollutingsubstances. A modern exhaust system comprises at least one mufflercomprising a tubular body, which typically displays an ellipticalsection and is provided with an inlet opening and an outlet opening. Alabyrinth which determines a path for the exhaust gases from the inletopening to the outlet opening is defined within the tubular body; suchlabyrinth is normally formed by diaphragms (or baffles) arrangedtransversally (i.e. perpendicularly to the longitudinal axis of thetubular body) to define chambers within the tubular body and by tubeswhich connect the chambers to each other.

In a traditional muffler, the counterpressure generated by the muffler(i.e. the loss of pressure determined in the exhaust gases by thepassage through the muffler) grows exponentially according as the enginespeed increases (i.e. as the average speed of the exhaust gasesincreases). Consequently, in order to avoid excessively highcounterpressure values at high engine speeds, it is necessary topenalise noise attenuation at low engine speeds. However, it would bepreferable if the counterpressure generated by the muffler were moreconstant at varying engine speeds so as obtain both a good noiseattenuation at low engine speeds and a limited counterpressure at highengine speeds.

In order to have a more constant counterpressure generated by themuffler at the variation of the engine speed, it has been suggested theuse of at least one bypass valve, which is controlled by pressure (i.e.is passive being without a motor member) and has the function ofmodifying the geometry of the muffler labyrinth according to the exhaustgas pressure (i.e. according to the engine speed). An example of abypass valve is provided in patent application WO2005059327A1.

A known bypass valve displays a lid, which is coupled to a bypassopening obtained through a diaphragm of the muffler and is mobile from aclosed position of the bypass opening to an opening position of thebypass opening by effect of the exhaust gas pressure and against thebias of a spring which tends to maintain the lid in the closed position.The most common solution provides that the lid is hinged onto thediaphragm of the muffler and is coupled to a torsional spring.

It has been observed that the known bypass valves display a limitedreliability in time, because the sliding couplings of the known bypassvalves (i.e. the hinging points of the lid and the turns of the spring)tend to get jammed or however to work in a different manner from thatprovided in the design step by effect of the incrustations formed by theexhaust gases.

DISCLOSURE OF INVENTION

It is the object of the present invention to provide a variable geometrymuffler for an exhaust system of an internal combustion engine, whichmuffler is free from the above-described drawbacks, and specifically iseasy and cost-effective to manufacture.

According to the present invention, a variable geometry muffler for anexhaust system of an internal combustion engine is provided as claimedin the attached claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to theaccompanying drawings, which illustrate some non-limitative examples ofembodiment thereof, in which:

FIG. 1 is a schematic and perspective view of a muffler made accordingto the present invention;

FIG. 2 is a schematic view of an internal labyrinth of the muffler inFIG. 1;

FIG. 3 is a side section view of a bypass valve of the muffler in FIG.1;

FIG. 4 is a schematic and perspective view of a different embodiment ofthe bypass valve in FIG. 3;

FIG. 5 is a schematic and perspective view of a further embodiment ofthe bypass valve in FIG. 3;

FIG. 6 is a side elevated view of the bypass valve in FIG. 5;

FIG. 7 is a perspective exploded view of the bypass valve in FIG. 5;

FIG. 8 is a schematic and perspective view of a further embodiment ofthe bypass valve in FIG. 3;

FIG. 9 is a side section view of the bypass valve in FIG. 8;

FIG. 10 is a plan view of an annular accommodation seat of a wire-meshring;

FIG. 11 is a section view taken along line XI-XI of a detail in FIG. 10;and

FIG. 12 is a section view take along line XII-XII of a detail in FIG.10.

PREFERRED EMBODIMENTS OF THE INVENTION

In FIG. 1, numeral 1 indicates as a whole a muffler 1 for an exhaustsystem of an internal combustion engine (not shown). Muffler 1 comprisesa tubular body 2, which displays an elliptical section and is providedwith an inlet opening 3, through which the exhaust gases produced by theinternal combustion engine enter tubular body 2, and an outlet opening4, through which the exhaust gases exit from tubular body 2.

As shown in FIG. 2, a labyrinth 5 which determines a path for theexhaust gases from inlet opening 3 to outlet opening 4 is defined insidetubular body 2. Labyrinth 5 consists of diaphragms 6 (or baffles)arranged transversally (i.e. perpendicularly to a longitudinal axis 7 oftubular body 2) to define chambers 8 within tubular body 2 and of tubes9 which connect chambers 8 to each other.

A bypass valve 10, which is adapted to modify the geometry of labyrinth5 according to the pressure of the exhaust gases is arranged withintubular body 2; specifically, in the embodiment shown in FIG. 2, bypassvalve 10 is coupled to a diaphragm 6 and according to the exhaust gaspressure is adapted to put two chambers 8 which are, normally,reciprocally isolated by diaphragm 6 itself into direct communication.

As shown in FIG. 3, bypass valve 10 comprises a lid 11, which is coupledto a bypass opening 12 and is mobile from a closed position (shown by asolid line in FIG. 3) of bypass opening 12 to an opening position (shownby a dotted line in FIG. 3) of bypass opening 12 by effect of theexhaust gas pressure and against the bias of an elastic body which tendsto maintain lid 11 in the closed position.

The elastic body consists of an elastic foil 13, which is folded as a“U” and displays a mobile end 14 coupled to lid 11 and a fixed end 15which is opposite to mobile end 14 and integral with a fixed part ofmuffler 1 (specifically with diaphragm 6 in which bypass valve 10 ismounted).

According to the embodiment shown in FIGS. 2, 3, 4, 8 and 9, mobile end14 of elastic foil 13 supports lid 11. According to the embodiment shownin FIGS. 2 and 3, lid 11 consists of an extension of mobile end 14 ofelastic foil 13 and forms a monolithic body with elastic foil 13 itself;instead, according to the embodiments shown in FIGS. 4, 8 and 9, mobileend 14 of elastic foil 13 is connected to lid 11 by means of rivets,fitting and/or welding. According to a different embodiment (not shown),mobile end 14 of elastic foil 13 supports lid 11 by means of theinterposition of a connecting element, which is fixed both to mobile end14 and to lid 11.

According to the embodiment shown in FIGS. 2 and 3, fixed end 15 ofelastic foil 13 is arranged by the side of bypass opening 12 and isdirectly fixed (typically screwed, riveted or welded) to diaphragm 6 inwhich bypass valve 10 is mounted.

According to the embodiments shown in FIGS. 4-9, fixed end 15 of elasticfoil 13 is arranged by the side of bypass opening 12 and is fixed to asupport 16 (typically screwed, riveted or welded) to diaphragm 6 inwhich bypass valve 10 is mounted. According to the embodiment shown inFIGS. 8 and 9, support 16 displays a flat plate, which is arranged overbypass opening 12 and displays a through hole 17 obtained at bypassopening 12 itself. According to the embodiments shown in FIGS. 4-7,support 16 is shaped as an inverted “U”.

According to the embodiment shown in FIGS. 5-7, lid 11 is hinged tosupport 16, which is fixed (typically screwed, riveted or welded) todiaphragm 6 in which bypass valve 10 is mounted; in this manner, lid 11is rotationally mounted to turn about an axis of rotation between theclosed position and the opening position. In this embodiment, mobile end14 of elastic foil 13 rests on lid 11, while fixed end 15 of elasticfoil 13 is coupled to (i.e. received by) support 16. Preferably, lid 11is hinged to support 6 by means of a hinge pin 18, which is integralwith support 16 (i.e. lid 11 turns with respect to pin 18); furthermore,elastic foil 13 partially envelops pin 18.

According to a preferred embodiment, bypass valve 10 comprises awire-mesh ring 19, which is arranged about bypass opening 12 to definean abutting element against which lid 11 rests in the closed position.According to the embodiment shown in FIGS. 2 and 3, bypass opening 12 isobtained through diaphragm 6, which displays an annular accommodationseat 20 of wire-mesh ring 19. According to the embodiment shown in FIGS.8 and 9, support 16 displays annular accommodation seat 20 of wire-meshring 19.

In the embodiment shown in FIGS. 2 and 3, wire-mesh ring 19 displays arectangular section and accommodation seat 20 consists of a “U”-shapedfold of diaphragm 6 squashed to clamp a lower portion of wire-mesh ring19. In the embodiments shown in FIGS. 8-12, wire-mesh ring 19 displays a“L”-shaped section and accommodation seat 20 is formed so as to clamp alower horizontal portion of wire-mesh ring 19.

FIGS. 10-12 show a possible embodiment of annular accommodation seat 20of wire-mesh ring 19; specifically, accommodation seat 20 shown in FIGS.10-12 consists of a plurality of portions 21 of diaphragm 6, each ofwhich is arranged to delimit bypass opening 12 and is deformed to catcha horizontal portion of wire-mesh ring 19. Portions 21 of diaphragm 6are alternatively deformed in opposite directions to catch oppositesides of the horizontal portion of wire-mesh ring 19.

The above-described Muffler 1 displays a number of advantages, becauseit is simple and cost-effective to make and at the same time displays ahigh reliability in time; such result is obtained in virtue of the factthat the use of elastic foil 13 allows to make bypass valve 10essentially insensitive to the incrustations formed by the exhaustgases.

1) A variable geometry muffler (1) for an exhaust system of an internalcombustion engine; the muffler (1) comprises: a tubular body (2), whichdisplays an inlet opening (3), an outlet opening (4) and a labyrinth (5)which determines a path for the exhaust gases from the inlet opening (3)to the outlet opening (4); and at least one bypass valve (10), which isarranged within the tubular body (2) to modify the geometry of thelabyrinth (5) according to the exhaust gas pressure; the bypass valve(10) comprising a lid (11), which is coupled to a bypass opening (12)and is mobile from a closed position of the bypass opening (12) to anopening position of the bypass opening (12) by effect of the exhaust gaspressure and against the bias of an elastic body which tends to maintainthe lid (11) in the closed position; the muffler (1) is characterised inthat the elastic body consists of an elastic foil (13), which is foldedas a “U” and displays a mobile end (14) coupled to the lid (11) and afixed end (15) which is opposite to the mobile end (14) and integralwith a fixed part of the muffler (1). 2) A muffler (1) according toclaim 1, wherein the mobile end (14) of the elastic foil (13) supportsthe lid (11). 3) A muffler (1) according to claim 2, wherein the mobileend (14) of the elastic foil (13) supports the lid (11) by means of theinterposition of a connecting element, which is fixed both to the mobileend (14) and to the lid (11). 4) A muffler (1) according to claim 1,wherein the fixed end (15) of the elastic foil (13) is arranged by theside of the bypass opening (12). 5) A muffler (1) according to claim 4,wherein the fixed end (15) of elastic foil (13) is fixed to a support(16), which is fixed to a fixed part of the muffler (1), is arrangedover the bypass opening (12) and displays a through hole (17) obtainedat bypass opening (12) itself. 6) A muffler (1) according to claim 1,wherein the lid (11) consists of an extension of the mobile end (14) ofthe elastic foil (13) and forms a monolithic body with the elastic foil(13) itself. 7) A muffler (1) according to claim 1, wherein the mobileend (14) of the elastic foil (13) is directly fixed to the lid (11) andthe fixed end (15) of the elastic foil (13) is fixed to a support (16)fixed onto a fixed part of the muffler (1). 8) A muffler (1) accordingto claim 7, wherein the support (16) is shaped as an inverted “U”. 9) Amuffler (1) according to claim 1, wherein the lid (11) is hinged to afixed part of the muffler (1) and the mobile end (14) of the elasticfoil (13) rests on the lid (11). 10) A muffler (1) according to claim 9,wherein a support (16), which is integral with a fixed part of themuffler (1), accommodates the fixed end (15) of the elastic foil (13),and supports a hinging pin (18) of the lid (11), is provided. 11) Amuffler (1) according to claim 10, wherein the pin (18) is integral withthe support (16) and the lid (11) turns with respect to the pin (18).12) A muffler (1) according to claim 10, wherein the pin (18) isintegral with the lid (11) and turns with respect to the support (16).13) A muffler (1) according to claim 10, wherein the elastic foil (13)partially envelops the pin (18). 14) A muffler (1) according to claim 1,wherein the bypass valve (10) comprises a wire-mesh ring (19), which isarranged about the bypass opening (12) to define an abutting elementagainst which the lid (11) rests in the closed position. 15) A muffler(1) according to claim 14, wherein the bypass opening (12) is obtainedthrough a diaphragm (6), which displays an annular accommodation seat(20) of the wire-mesh ring (19). 16) A muffler (1) according to claim15, wherein the wire-mesh ring (19) displays a rectangular section; theaccommodation seat (20) consists of a “U”-shaped fold of the diaphragm(6) squashed to clamp a lower portion of the wire-mesh ring (19). 17) Amuffler (1) according to claim 15, wherein the wire-mesh ring (19)displays an “L”-shaped section; the accommodation seat (20) consists ofa plurality of portions of the diaphragm (6) each of which is arrangedto delimit the bypass opening (12) and is deformed to catch a lowerhorizontal portion of the wire-mesh ring (19). 18) A muffler (1)according to claim 17, wherein the portions (21) of the diaphragm (6)are alternatively deformed in opposite directions to catch oppositesides of the horizontal portion of the wire-mesh ring (19). 19) Avariable geometry muffler (1) for an exhaust system of an internalcombustion engine; the muffler (1) comprises: a tubular body (2), whichdisplays an inlet opening (3), an outlet opening (4) and a labyrinth (5)which determines a path for the exhaust gases from the inlet opening (3)to the outlet opening (4); and one bypass valve (10), which is arrangedwithin the tubular body (2) to modify the geometry of the labyrinth (5)according to the exhaust gas pressure; the bypass valve (10) comprises alid (11), which is coupled to a bypass opening (12) obtained through adiaphragm (6) and is mobile from a closed position of the bypass opening(12) to an opening position of the bypass opening (12) by effect of theexhaust gas pressure and against the bias of an elastic body which tendsto maintain the lid (11) in the closed position, and a wire-mesh ring(19), which displays an “L”-shaped section and which is arranged aboutthe bypass opening (12) to define an abutting element against which thelid (11) rests in the closed position; the muffler (1) is characterisedin that the diaphragm (6) displays an annular accommodation seat (20) ofthe wire-mesh ring (19) formed by a plurality of portions (21) of thediaphragm (6), each of which is arranged to delimit the bypass aperture(12) and is deformed to catch a horizontal portion of the wire-mesh ring(19). 20) A muffler (1) according to claim 19, wherein the portions (21)of the diaphragm (6) are alternatively deformed in opposite directionsto catch opposite sides of the horizontal portion of the wire-mesh ring(19).